Piezoelectric igniter for projectiles



Dec. 5, 1967 .1. LUBIG 3,356,026

PIEZOELECTRIC IGNITER FOR PROJECTILES Filed Nov. 10, 1964 5 Sheets-Sheet 1 PIEZOELECTRIC IGNITER FOR PROJECTILES Filed NOV. 10, 1964 3 Sheets-Sheet 2 F/GZ 5: a Lab,- BY

Dec. 5, 1967 J. LUBIG 3,356,026

PIEZOELECTRIC IGNITER FOR PROJECTILES Filed Nov. 10, 1964 3 Sheets-Sheet 5 INVENTOR United States Patent 3,356,026 PIEZOELECTRIC IGNITER FOR PROJECTILES Josef Lubig, Bad Godesberg, Germany, assiguor to Dynamit Nobel A.G., Bezirk Cologne, Germany Filed Nov. 10, 1964, Ser. No. 410,081 8 Claims. (Cl. 102-702) The present invention concerns an electrical fuse assembly for missiles of any kind no matter whether they are artillery shells, bombs, dropped by aircraft, rockets fired from the ground, from the air or from shipboard etc. More specifically, the invention concerns electrical fuse assemblies which comprise piezoelectric means for producing the electric igniting impulse.

The main purpose of the invention is to provide for an electrical fuse assembly of the above kind which is more sensitive than conventional electrical fuses and practically safe against failures, while at the same time the fuse assembly according to the invention is intended to be suitable for being used in more different applications than conventional fuses.

Conventional piezoelectric fuse devices are useful exclusively as impact detonators and usually fail when the trajectory of the missile is inclined at the point of impact with respect to the surface at the impact point at an angle differing greatly from the perpendicular.

Many attempts have been made to improve the performance of piezoelectric fuses, but no satisfactory solution has been found up to now.

It is therefore one object of this invention to provide for an electrical fuse assembly for missiles which contains piezoelectric means but is nevertheless very simple in its construction.

It is another object of this invention to provide for a fuse assembly of the type set forth which is comparatively easy to produce and to assemble.

it is another object of this invention to provide for an electrical fuse assembly as mentioned above which reacts extremely sensitively to those conditions which are supposed to cause ignition of the detonator.

It is still another object of the invention to provide for a fuse assembly as set forth which additionally contains a mechanical safety device.

With these objects in view the invention includes an electrical fuse assembly for missiles, which comprises, in combination, a fuse body having a cavity and an axis, detonator means mounted on said body, electric fuse means mounted in said body adjacent to said detonator means, piezoelectric means mounted in said cavity of said fuse body and including a piezoelectric element and conductively connected with said electric fuse means for energizing the latter when said piezoelectric element is subjected to a predetermined minimum amount of pressure, and inertia means including an inertia body arranged in said cavity of said fuse body adjacent to said piezoelectric element with a predetermined amount of freedom of movement relative to said element for exerting said predetermined amount of pressure on said element when one of said bodies is accelerated relative to the other in the direction of said axis.

It should be understood that the fuse assemblies according to the invention mainly operate in response to the inertia of a member of the assembly and that it is not necessary to provide for the inertia body of the assembly to be able to carry out a substantial amount of movement in response to positive or negative acceleration. Experiments have shown that very small fractions of a millimeter down to a few microns are sufiicient. As a matter of fact, it is even desirable to limit the freedom of movement of the inertia body of the assembly to a minimum so that the reaction time and the sensitivity of the fuse assembly will meet the most exacting conditions.

It will be seen also that an electrical fuse assembly according to the invention distinguishes from most known similar devices by the fact that no wires or circuits have to be incorporated in the fuse assembly because the components thereof will constitute themselves the necessary conductors for energizing an electrical fuse.

It will be seen that in certain cases the fuse assembly according to the invention can be modified in such a manner that the entire assembly can function both as a fuse reacting to the inertia of a component of the assembly whenever positive or negative acceleration occurs, but also as an impact detonator.

The invention includes various modifications so that certain embodiments of the invention may be used as tail fuses and others as nose fuses just as a particular type of missile may require.

The novel features which are characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIG. 1 is a diagrammatic illustration, partly in axial section of one embodiment of the invention which is a purely intertia-responsive fuse well suited for artillery shells of any kind with a safety device in normal position;

FIG. 2 is a similar illustration of the fuse according to FIG. 1 in armed condition;

FIG. 3 is a diagrammatic illustration similar to FIG. 2, partly in axial section, of another embodiment of the invention which is also useable as an inertia-responsive fuse which responds both to the acceleration at the moment of firing the shell or missile and to the reverse acceleration upon impact; and

FIG. 4 is another embodiment of the invention which is intended to serve mainly as an impact detonator but additionally utilizes the effect of inertia.

Referring now to FIG. 1 it is to be understood that the fuse assembly illustrated thereby is designed to be rigidly mounted in the base or tail portion of a missile, and includes a mechanical safety or automatic arming device. The assembly comprises a fuse body which is composed of front portion 1 and a rear portion 1a screwed together and which may be made entirely of metal, i.e., of electrically conductive material, or at least have a portion made of conductive material because the respective portion or the entire body will constitute a part of the electric circuit of the assembly as will be explained further below. The body portion 1 carries a conventional detonator 8 closed by a cap 8" and holding a charge 8 and a conventional electric fuse 7 carried in the rotor 10 of a safety device described below and located, in the position thereof shown by FIG. 2, immediately adjacent to the detonator 8 so that when the fuse 7 is electrically energized it will cause detonation of the detonator 8.

The above mentioned safety device comprises first of all a rotor 10 supported in the body portion 1 for rotation about an axis transverseof the longitudinal axis of the body and having, concentric with said axis of rotation, a stem 10' projecting outwardly through a corresponding transverse bore 12" of an anular member 12 also concentric with said axis of rotation and inserted in body portion 1 as shown. The inner face of the annular member 12 facing the one lateral face of the rotor 10 is provided with a circular groove 12 extending through an arc of substantially 270, and the rotor 10 carries a stop pin 11 projecting into said groove 12'. A torsion spring- 13 surrounds the stem 10 which is split at 10" for accom modating one tail end of spring 13, the other end of which is fixed in the annular member 12 as shown. During assembly the member 12 is rotated about 540 relative to the rotor so that spring 13 is correspondingly tensioned while rotor 10 is in the illustrated position of FIG. 1 in which the axis of the electric fuse 7 is oriented transversely of the axis of the fuse body. In this position of the annular member 12 a locking screw 14 is positioned to project into a corresponding recess 14 of the member 12 whereby the latter is fixed in position.

Now the rotor 10 is subject to a considerable torque produced by spring 13, but is prevented from turning by a ball 18 positioned in a slanting bore 1b of the body portion 1 and projecting somewhat into a corresponding recess 10a of the rotor A further portion of the safety device is an inertia control device comprising an inertia body 19 having the shape of a bolt with a head portion and a fine-threaded shank movable in axial direction in a corresponding hollow ortion of body portion 1. A spring 17 located within the hollow shank of member 19 and guided at its lower end in a guide box 16 urges the member 19 forward so that it normally occupies the position illustrated in FIG. 1 in which case the head portion thereof prevents the ball 18 from leaving the recess 1b.

As can be Seen from FIGS. 1 and 2, the electrical fuse 7 has an outer shell which constitutes one terminal thereof and which is in contact with the surface of the bore of rotor 16 which holds the fuse 7, and has a second terminal a pin 7 which in the position of FIG. 1 is not visible and projects into the hollow space inside the body portion 1, but in the arming position of FIG. 2 projects in axial direction for contacting a slide member composed of an outer mem er 21 slidablo in t e corresponding aXial Channel of body portion 1, and an inner member 20 which accommodates one end of a compression spring 22 which urges the slide 2.0. 21 into con t with the circumference of rotor 19 n po i n of FIG- 1) and with the fus pin 7' .(in position of FIG. 2).

The operation of h safe y d vice i as follo When the missile which contains the fuse assembly illustrated by FIGS. 1 and 2 is fired the inertia body 19 will be held back by inertia and will compress the spring 17, thus having its head portion moved to a position in which the recess 1 is clear and the all 1 is permitted to drop in the hollow space in front of the body 19. Consequently the rotor 10 is now free to rotate about 270" under the action of the torsion spring 13 until the stop pin 11 abuts against the end of the groove 12'. Now the rotor is in the position shown by FIG. 2 and the fuse assembly is armed since the front end of the electrical fuse 7 is immediately adjacent to the .detonator 8 while the fuse Pin 7' is in contact with the contact tip of slide 20, 21. In order to prevent a ci en al arming of the f se ass mbly by minor shocks, the shank of the inertia body 19 is provideo with a fine thread, and a metal washer 15 is placed on top of the guide body 1.6 and provided with a precise and sharp-ed ed c nter hole closel fitting he te d ameter of the thread of the shank .of body 19 so that a substantial frictional resistance is set up by the engagement between thread and washer sufficient to prevent accidental movement of the body 19. However, the force of inertia developing upon firing the missile is amply sufficient for overcoming the frictional resistance of the washer 15. The body portion 1 1 contains a cavity in which the other components of the fuse assembly according to the invention are located. As can be seen there is located in the body cavity a conventional piezoelectn'c element 5 preferably formed as a thin plate sandwiched between a contact plate 2 of conductive material and an inertia body 3 also of conductive material. The components 2 and 5 are surrounded by an insulating lining 6 so as to be insulated against the conductive portions of the body 1, 1a. By means of a screw 4 in thread engagement with the edge of the body cavity the members 2,

3, 5 and 6 are firmly held in position within the body. A pin 2 projecting from plate 2 holds the surrounding spring 22 in contact with plate 2 for electrically connecting the latter with the fuse pin 7 which is a terminal of the electrical fuse 7. For safetys sake and for practical purposes it may be advisable to arrange a spring 24 in a recess of the inertia body 3 or of the screw 4 as shown in order to assure good electrical contact between the screw 4, the inertia body 3, the piezoelectric element 5, the contact plate 2 and the fuse pin 7' of the fuse 7. A cushioning washer 23 may also be provided as shown. It can be seen that therefore an electrical circuit is established in the armed position of FIG. 2, between the above mentioned components and via screw 4 and body 1, 1a for energizing the electrical fuse 7, whenever the piezoelectric element 5 is subjected to at least a predetermined minimum amount of pressure for generating an electric potential sufiicient to energize the fuse 7.

In operation, upon deceleration of the missile or in other words, upon acceleration of the inertia body 3 relative to the body 1, 1a or relative to the piezoelectric element 5, the latter is subjected at least to a predetermined minimum amount of pressure whereby the electric energy is generated and applied to the fuse 7 which is needed for energizing the latter and thus to cause detonation of the detonator 8.

As mentioned above, the inertia body 3 requires very little freedom of movement in the axial direction of the assembly for exerting the above-mentioned pressure on the element 5, as a rule a movement of the order of one or several microns is sufilcient.

The embodiment of the invention illustrated by FIG. 3 is also designed to be mounted in the base or tail portion of the missile. The description given above applies analogously to the body 1, 1a, the detonator 3 and the electric fuse 7. Also the safety device is the same as described above. Therefore FIG. 3 shows this second embodiment only in armed condition. However, in this case the cavity of the body portion in has an insulating lining 6a which surounds the piezoelectric element 5 sandwiched between a contact plate 2a of conductive mat i d an in a b dy 41 also of conducti e material, the inertia body So being located in this case on the forward side of the element 5 and carrying a pin 3a projecting forward through an opening of the lining 6a and having together with spring 22 the same function as members 2' and 22 in the first embodiment. An insulating disc 6b having a central hole covers the contact plate 2a and insulates the latter from the adjacent portions of the body portion 1a and from a screw insert 25 which is in thread engagement with the rear end of the body cavity so that by screwing this insert 25 into the cavity the above-described group of components 5, 2a, 3a, 6a and 66 is firmly held in position in the body 1, 1a. The screw insert 25 has a recess closed by a screw member 4a which, in turn, is provided with a central threaded hole which accommodates a set screw 28. The recess or cavity of the member 25 has an extension of preferably cylindrical form in register with the central hole of the insulating disc 66 as illustrated. A second inertia body 26 having the shape of a pin is arranged in said cavity of the member 25 so as to be freely movable in axial direction be tween the position of rest illustrated in FIG. 3, and a second position in which the forward end of the pin 26 contacts the face of the contact plate 2a. The member 26 is provided with a flange 26a and a coil spring 27 is interposed between the front wall of the recess of member .25 and the top face of the flange 26a whereby the second inertia body 26 is normally held in the illustrated position of rest.

It will be understood that upon firing the missile, the body 1, la will be accelerated relative to the inertia body 3a, so that hereby the required pressure is exerted on the piezoelectric element 5 for generating a predetermined amount of electric potential. Since the conductive members 2a and 3a surrounding the piezoelectric element 5 are insulated from the conductive portions of the body 1, 1a, and the other elements, the group of components 5, 2a, 3a function as a capacitor which assumes a charge corresponding to the electric potential generated by pressure in the piezoelectric element 5. This charge will disappear when the acceleration of the body ceases. During flight the missile willl be decelerated due to air resistance and the inertia body 3a will become disengaged from the piezoelectri element. When now in the further course of events the missile is suddenly further decelerated by impact of the missile on a target, then the sudden impulse Will cause deformation of the transverse wall of the insulation lining 6a so that the inertia body will rebound and press with great force against one face of the piezoelectric element 5, while at the same time the second inertia body namely the pin 26 will be accelerated relative to the body 1, 1a, and therefore overcome the counteraction of the spring 27 and move forward into contact with the contact plate 2a so as to press the latter against the other face of the element 5. At this moment a circuit is closed for discharging the charge produced by the pressure in the element 5, this circuit being composed of the contact plate 2a, the pin 26, spring 27, insert 25, body portions 1, 1a or their conductive portions, rotor 10, the fuse 7, the fuse pin 7', slide member 20, spring 22 and the first inertia body 3a. The discharge of the charge results in the energization of the fuse 7 which causes the detonation of the detonator 8.

The third embodiment illustrated by FIG. 4 is chiefly designed to be a fuse assembly to be mounted in the nose of the missile. Therefore, it is intended to be responsive to the impact of the missile on the target but is nevertheless also provided with means for utilizing the inertia of an inertia body for energizing the piezoelectric element of the assembly. The embodiment of FIG. 4 comprises also the safety device described above and therefore FIG. 4 illustrates this device in armed condition only diagrammatically, showing in dotted lines the rotor 10, the fuse 7 and its fuse pin 7, the slide 21 and connecting spring 22. As can be seen the body 1' which has at least a conductive portion where needed or is entirely conductive is equipped with a detonator 8 and an electric fuse 7 as mentioned above mounted in the safety device rotor 10 and positioned, in armed condition, adjacent to the detonator 8 in the body 1. At its forward end the body 1 is again provided with a cavity which has an insulating lining 6c surrounding a piezoelectric element 5 sandwiched between an inertia body 36 of conductive material and an impact body 30 also of electrically conductive material. An impact cover 29 also of conductive material is mounted so as to coverthe front end of the entire assembly and is connected with the body 1' by a thread engagement as illustrated. The

fuse pin 7', slide 21 and spring 22 are provided for connecting the inertia body 26 with the fuse 7 in the manner generally described further above.

In assembling this arrangement the impact cover 29 will be screwed onto the body 1' until it engages lightly the forward tip of the impact body 30 just suificiently for holding the components mentioned above in place. Of course, the pressure exerted by screwing the impact cover 29 onto the body 1 should not reach a magnitude that would subject the piezoelectric element 5 to a pressure whereby a substantial electric potential would be generated. The impact cover 29 should be provided with predetermined relatively weak wall portions in the area 29a so that upon impact of the forward end of the impact cover 29 upon a target immediate buckling of the walls of the impact cover 29 is assured because under these circumstances it can be reliably expected that immediately the inside wall of the front end of the cover 29 will exert pressure on the impact body 30, and this in turn will produce the required pressure forcausing the piezoelectric current 5 to generate the potential which is required for energizing the fuse 7. The circuit for causing this energization is established through the body 1' and the cover 29 in the same manner as described further above.

It should be noted however, that even in those cases Where the direct impact of the missile on a target should be for any reason unsuitable for causing the abovedescribed energization of the fuse assembly, but nevertheless, a deceleration of the missile or of the fuse assembly should be caused, then under all circumstances the inertia body 36 would be accelerated relative to the body 1' and still exert the required pressure on the element 5 for causing the latter to furnish the electric potential which in the manner described above would still cause detonation of the detonator 8.

It will be understood that the electrical fuse assembly according to the invention creates additional advantages beyond those already described above. It can be seen readily for instance that in contrast to conventional fuse assemblies the fuse assembly according to the invention does not require a detonating canal reaching from a nose fuse all the way through the missile to a detonator or buster charge located in the tail end of the missile. Consequently, there is more space available in the missile for accommodating the actual explosive charge and the explosion of this charge will be much more eflicient because the entire charge has a more homogeneous structure in view of the missing central canal.

Moreover, the elimination of the ignition flash which has to carry the ignition from the nose of the missile to the detonator or buster charge at the tail end the entire ignition process is favorably influenced because, if the fuel assembly according to the invention is mounted in the base or tail portion of the missile, the detonation is started exactly there where it is to be applied directly to the explosive charge. In this manner the ignition process is accelerated and the efiiciency of the missile is increased.

In particular it should be noted that the assembling procedure of a fuse assembly according to the invention in much simpler andeasier than in the case in conventional assemblies of this kind because no wiring of any kind is necessary. The components of the ignition assembly constitute themselves the circuit components for the electrical equipment of the fuse.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of electrical fuse assemblies from missiles, differing from the types described above.

While the invention has been illustrated and described as embodied in an electrical fuse assembly for missiles including piezoelectric means and at least one inertia body adapted to act on that piezoelectric means, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that. others can, by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. Electrical fuse assembly for missiles, comprising, in combination, a fuse body having a cavity and an axis, at least a portion of said fuse body being electrically conductive; detonator means mounted on said body; electric fuse means mounted in said body cavity adjacent to said detonator means and having two terminals one of which is in contact with said conductive portion of said fuse body; piezoelectric means mounted in said cavity of said fuse body and including a piezoelectric element and a contact plate of conductive material in engagement with one side of said element, said element and said plate being insulated from said body, said piezoelectric means being adapted to produce an electric potential for energizing said electric fuse means when said piezoelectric element is subjected to a predetermined minimum amount of pressure; and inertia means including a first inertia body of conductive material arranged in said cavity insulated therefrom but adjacent to the other side of said piezoelectric element with a predetermined amount of freedom of movement relative thereto for exerting said predetermined amount of pressure on said element when said fuse body is decelerated relative to said first inertia body in the direction of said axis so that a corresponding charge is built up between said contact plate and said first inertia body, and a second inertia body of conductive material movable within said cavity of said fuse body in contact therewith, said second inertia body being normally out of contact with said contact plate and being movable into contact with said contact plate when said second inertia body is accelerated in direction of said axis relative to said fuse body so that said charge is released so as to energize said electric fuse means, and conductor means connecting said first inertia body with the other terminal of said electric fuse means.

2. Electrical fuse assembly for missiles, comprising, in combination, fuse body means having a cavity and a longitudinal axis at least a portion of said fuse body means being electrically conductive; detonator means mounted in said body means; electric fuse means in said body means for igniting, when electrically energized, said detonator means, said fuse means having two terminals; piezoelectric means mounted in said cavity of said fuse body and including a piezoelectric element and a contact plate in contact with one side of said element and being conductively connectible with said electric fuse means for energizing the latter when said piezoelectric element is subjected to a predetermined minimum amount of pressure, said piezoelectric element and said contact plate having one face insulated from said fuse body means; mechanical safety means for keeping said fuse assembly normally inoperative and for arming said fuse assembly only when the latter is subjected to acceleration forwardly in direction of said axis and comprising at least one I tary member of conductive material carrying said electric fuse means in conductive contact with one terminal thereof and being movable relative to said fuse body means in response to such acceleration from a first position in which said electric fuse means is kept spaced from said detonator means and conduction of electricity between said piezoelectric element and said electric fuse means is prevented to a second position in which said electric fuse means is placed immediately adjacent to said detonator means and a direct conductive connection between one side of said element and the other terminal of said fuse means is established by rotary movement of said member, movable locking means locking said rotary member in said first position, an inertia-responsive member releasing said locking means from said locking position in response to acceleration of said fuse assembly; and means for moving said rotary member from said first to said second position when said locking means is released; and inertia means including a first inertia body of conductive material arranged in said cavity of said fuse body and insulated therefrom but adjacent to said one side of said piezoelectric element with a predetermined amount of freedom of movement relative to said element in direction of said axis for exerting said predetermined amount of pressure on said element when one of said bodies is decelerated relative to the other in direction of said axis so that a corresponding charge is built up between said contact plate and said first inertia body, and a second inertia body of conductive material movable within said cavity of said fuse body means in conductive connection therewith, said second inertia body being normally out of contact with said contact plate and being movable into contact with said contact plate when said second inertia body is accelerated forwardly in direction of said axis relative to said fuse body means so that said charge is released so as to energize said electric fuse means.

3. Electrical fuse assembly for missiles, comprising, in combination, fuse body means having a cavity and a longitudinal axis; detonator means mounted in said body means; electric fuse means in said body means for igniting, when electrically energized, said detonator means; piezoelectric means mounted in said cavity of said fuse body and including a piezoelectric element and being conductively connectible with said electric fuse means for energizing the latter when said piezoelectric element is subjected to a predetermined minimum amount of pressure; mechanical safety means for keeping said fuse assembly normally inoperative and for arming said fuse assembly only when the latter is subjected to acceleration forwardly in direction of said axis and comprising at least one rotary member carrying said electric fuse means and being movable relative to said fuse body means in response to such acceleration between a first position in which said electric fuse means is kept spaced from said detonator means and conduction of electricity between said piez0 electric element and said electric fuse means is prevented and a second position in which said electric fuse means is placed immediately adjacent to said detonator means and conductive connection between said element and said fuse means is established by rotary movement of said member, movable locking means locking said rotary member in said first position, an inertia-responsive member releasing said locking means from said locking position in response to acceleration of said fuse assembly, and means for moving said rotary member from said first to said second position when said locking means is released; and pressure exerting means including an inertia body of conductive material arranged in said cavity and insulated therefrom but located adjacent to one side of said piezoelectric element and conductor means connecting said inertia body with the other terminal of said electric fuse means when said safety device is in said second position, and an impact body of conductive material arranged in said body cavity and adjacent to the other side of said piezoelectric element, and an impact cover mounted in a position closing said body cavity and having a portion closely covering said impact body, both said inertia body and said impact body having a limited amount of freedom of movement realtive to said piezoelectric element for exerting said predetermined amount of pressure on said one side of said piezoelectric element when said inertia body is accelerated forwardly in the direction of said axis relative to said element and for exerting said pressure on the other side of said element when said piezoelectric element is accelerated in the direction of said axis relative to said impact body due to impact of said impact cover on a target.

4. An electrical fuse assembly according to claim 3, wherein said impact cover is provided with predetermined weakened wall portions facilitating breakage of said impact cover and immediate pressure exertion on said impact body and thereby on said piezoelectric element when said impact cover hits a target.

5. Electrical fuse assembly for missiles comprising, in combination, a fuse body having a cavity and an axis: detonator means mounted on said fuse body; electric fuse means mounted in said body adjacent said detonator means; a transverse wall of insulating material extending transversely through said cavity; a piezoelectric element;

a first electrically conductive component to one side of said element; a second electrically conductive component in form of an inertia body at the other side of said element, said piezoelectric element and said two components being arranged in said cavity slidable in axial direction with one of said components adjacent said transverse wall; electrically conductive spring means extending through an opening of said transverse wall between said fuse means and one of said components and being biased so as to resiliently keep said one component spaced from said transverse wall, whereby when one of said bodies is accelerated relative to the other in direction of said axis, said one component will be pressed against said transverse wall and said piezoelectric element will be subjected to pressure between said two components so as to energize said fuse means.

6. An electrical fuse assembly as set forth in claim 5, wherein said first electrically conductive component is in the form of a contact plate arranged adjacent said transverse wall and wherein said inertia body is in direct electrical contact with said fuse body.

7. An electrical fuse assembly as set forth in claim 5, wherein said inertia body is arranged adjacent said transverse wall, wherein said first component is in the form of a contact plate, and including a second transverse wall of insulating material, said contact plate normally abutting against one side of said second transverse wall, said second transverse wall being formed with an opening therethrough, a second electrically conductive inertia body aligned with said opening and arranged on the other side of said second transverse wall and having a portion adapted to move through said opening into contact with said contact plate, and additional electrically conductive spring means engaging said fuse body and said second inertia body and being biased so as to resiliently maintain said additional inertia body spaced from said contact plate.

8. An electrical fuse assembly as set forth in claim 5, wherein said inertia body is arranged adjacent said transverse wall and wherein said first component is in the form of a solid impact body, and including an impact cover mounted in a position closing said body cavity and having a portion in contact with said impact body.

References Cited UNITED STATES PATENTS 2,853,011 9/1958 Will et al 102-702 2,891,479 6/1959 Alexander et al. 102-70.2 2,894,457 7/1959 Severance 10270.2 2,934,017 4/1960 Ellet 102-70.2 2,972,306 2/ 1961 Kabik et al. 102-702 2,991,716 7/1961 Israel et a1 102-70.2 3,202,100 8/1965 Vilbajo 102--70.2

FOREIGN PATENTS 909,549 10/ 1962 Great Britain.

SAMUEL W. ENGLE, Primary Examiner.

BENJAMIN A. BORCHELT, Examiner.

W. C. ROCH, Assistant Examiner. 

5. ELECTRICAL FUSE ASSEMBLY FOR MISSILES COMPRISING, IN COMBINATION, A FUSE BODY HAVING A CAVITY AND AN AXIS; DETONATOR MEANS MOUNTED ON SAID FUSE BODY; ELECTRIC FUSE MEANS MOUNTED IN SAID BODY ADJACENT SAID DETONATOR MEANS; A TRANVERSE WALL OF INSULATING MATERIAL EXTENDING TRANSVERSELY THROUGH SAID CAVITY; A PIEZOELECTRIC ELEMENT; A FIRST ELECTRICALLY CONDUCTIVE COMPONENT TO ONE SIDE OF SAID ELEMENT; A SECOND ELECTRICALLY CONDUCTIVE COMPONENT IN FORM OF AN INERTIA BODY AT THE OTHER SIDE OF SAID ELEMENT, SAID PIEZOELECTRIC ELEMENT AND SAID TWO COMPONENTS BEING ARRANGED IN SAID CAVITY SLIDABLE IN AXIAL DIRECTION WITH ONE OF SAID COMPONENTS ADJACENT SAID TRANSVERSE WALL; ELECTRICALLY CONDUCTIVE SPRING MEANS EXTENDING THROUGH AN OPENING OF SAID TRANSVERSE WALL BETWEEN SAID FUSE MEANS AND ONE OF SAID COMPONENTS AND BEING BIASED SO AS TO RESILIENTLY KEEP SAID ONE COMPONENT SPACED FROM SAID TRANSVERSE WALL, WHEREBY WHEN ONE OF SAID BODIES IS ACCELERATED RELATIVE TO THE OTHER IN DIRECTION OF SAID AXIS, SAID ONE COMPONENT WILL BE PRESSED AGAINST SAID TRANSVERSE WALL AND SAID PIEZOELECTRIC ELEMENT WILL BE SUBJECTED TO PRESSURE BETWEEN SAID TWO COMPONENTS SO AS TO ENERGIZE SAID FUSE MEANS. 